On Tue, 28 Nov 2006, xiaoxin liu wrote:

> > Did you remember to make a USBDEVFS_REAPURB ioctl call?
> >
> >   
> I did't make a USBDEVFS_REAPURB ioctl call. Must I make this call??

Yes.  URBs don't complete immediately; it takes time for the device to 
send data to the computer.  USBDEVFS_REAPURB will wait until the transfer 
is complete.  If you don't wait then of course you won't see any data.

> > Are you certain the camera was trying to send ISO data?
> >
> >   
> Currently, I only know the camera is powered on. So I created a ISO 
> transfer URB to the webcam, I think it should reply some data to me. 
> What I want to do is to let the webcam reply to me.

According to the USB specification, the default altsetting for any 
interface should not send transfer any ISO data.  You might need to do 
a USBDEVFS_SETINTERFACE call.

Alan Stern


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